With the development of the display technology, much emphasis has been laid upon display quality of a display device. Quantum dots (QDs) can be spherical or roundish semiconductor nanoparticles consisting of II-VI group or III-V group elements, whose sizes are between 0 to 100 nanometers. Quantum dots show quantum confinement effect as sizes of particles are smaller than Bohr radius of exciton of corresponding bulk material, the energy level structure changes from quasi continuousness of bulk material to discrete structure of quantum dot material, which leads to quantum dots show a specific property that can be lit by radiation. Widths between energy levels increase according to decreasing sizes of quantum dots, energies required to stimulate corresponding quantum dots and energies released to return to the ground state of stimulated quantum dots are ascending accordingly, resulting in stimulation of quantum dots and blue shift phenomenon of fluorescence spectrum, luminescence spectrum can cover the whole visible region by controlling sizes of quantum dots. Such as a size of cadmium selenide (CdSe) descends from 6.6 nm to 2.0 nm, the according wavelength of light from red light region 635 nm ‘blue shifts’ to 460 nm of blue light region.
Quantum dots materials applied in display devices can significantly increase the color gamut of a display device and the ability of color reproduction. Until now, a number of papers and patents have published application of thin film transistor liquid crystal display (TFT-LCD) with quantum dots, in which quantum dots taking the place of conventional color film materials of TFT-LCD draws the most attention. Quantum dots substituting conventional color photoresistance can improve color gamut and penetration rate of TFT-LCD significantly, achieving better effects in display.
However, following problems exist in photoresists produced by quantum dot compound resin applied in manufacturing quantum dot color films: first, quantum dots are poor in heatproof, a conventional TFT photoresist process has to survive in a temperature more than 200 degrees, the heating temperature of a quantum dot photoresists needs to be curbed to make available quantum dot photoresists, which distinguishes ingredients of a quantum dot photoresist and that of a conventional photoresists, resulting in more research costs; second, quantum dots are pricy as well as toxic, amounts of quantum dots washed off during the developing step in a photoetching process are wasteful, further pollute the environment; third, application of quantum dot photoresists costs two or three photoetching processes which are expensive.
Color filter on array (COA) technology is a technique that disposing a color layer on an array substrate and forming a color filter film. Difficulties in alignment when manufacturing a display panel can be deducted due to aligning a color film substrate and an array substrate disappears in a display panel of COA structure, errors during alignment can be avoided, hence black matrixes can be designed to be a narrow line width to increase an aperture opening ratio.